Kumar is the latest in a surprising exodus of senior Republican staffers that has worried people in both parties and darkened the outlook for the confrontation this fall.

In addition to losing Kumar, McConnell has lost his longtime floor general, Dave Schiappa, who left after nearly three decades to take a job as vice president at the Duberstein Group, a downtown lobbying firm.

Kumar, a 13-year veteran from Dallas who got his start with former senatorPhil Gramm and has since served a series of Senate leaders, has been at McConnell's side through every major fiscal deal since President Barack Obama took office.

He is taking time off to be a stay-at-home dad to his 3-year-old daughter, Kiera.